Yeah it sucks that Microsoft don't provide exact numbers themselves, but ultimately they still provide the numbers that matter the most: division quarterly and annual revenue results. And from those we can extrapolate (to a good, reliable extent) hardware sales, especially when they provide hardware sales rates (such as certain YOY quarterly gain rates compared to same quarter in the previous year, etc.).
That's how I'm assuming guys like Welfare, Zhuge etc. are getting their numbers. They might also be shareholders, and shareholders, IIRC, get more info than what bits we end up getting reported on and quoted around online. So they can work with that data, as well.